Japanese Unexamined Patent Publication No. 158137/1999 discloses a compound represented by the formula (A): wherein R4 and R5 represent halogen, substituted or unsubstituted alkyl, or substituted or unsubstituted alkenyl; Y′ represents ═C(R6)— or ═N—; R6 represents hydrogen, halogen, alkyl or haloalkyl; m′ is an integer of 0 to 5; and n′ is an integer of 1 to 4. The compound represented by the formula (A) is a compound exhibiting keto-enol tautomerism as illustrated in the following formula. 
Said publication also discloses that the compounds represented by the formula (A) are useful as intermediates for preparing the acrylonitrile compounds represented by the formula (B): wherein R7 represents alkyl, haloalkyl or the like; and R4, R5, m′ and n′ are as defined above.
Further, said publication discloses that the compounds represented by the formulas (A) and (B) exhibit miticidal activities.
However, said publication merely teaches in the examples that the compounds represented by the formula (A) exhibit miticidal and ovicidal activities for two-spotted spider mites when used at a high concentration of 800 ppm.
The present inventors have confirmed through experiments that the compounds represented by the formula (A) exhibit little miticidal and ovicidal activities for two-spotted spider mites when used at a low concentration.
In addition, although said publication discloses that the acrylonitrile compounds represented by the formula (B) are effective for mite control, the miticidal activities thereof are not satisfactory. Thus, in consideration of the life cycle of mites, the demand exists for a miticide that can control the damage caused by mites over a long period of about 14 to about 40 days depending on factors such as the kind of mite, the type of plants to which the miticide will be applied, etc. However, the acrylonitrile compounds represented by the formula (B) are not effective for controlling the damage caused by mites over a long period of about 14 to about 40 days.
Recently, some mites have developed resistance to the miticides that have been in use for many years, making it difficult to control them with conventional miticides. Thus, there are demands for the development of a novel miticide that can give excellent mite control.